Sri Lanka is a continental island of the Indian subcontinent, shaped like a teardrop
falling from the southern end of India, situated between longitudes 79º 39E and 81º 53E and latitudes 5º 54N and 9º 52N. It's 437km long from north to south and only 225km at its widest. Its area
of 66,000sq km is about the same size as Ireland. The south-central region is mountainous and has an elevation ranging from 900m to 2440m. This is surrounded by an upland belt of 300-900m
elevation. The coastal plains hardly exceed 100m in elevation. This plain is most extensive in the north and east, and the continental shelf ends fairly close to the shoreline except in the
northwest where it is continuous with that of India. Today Sri Lanka is considered one of the most bio-diverse areas in South Asia. Recent scientific evidence indicates that many of the plants
species in the southwest of the country have a Deccan-Gondwana ancestry.

The drainage pattern of the country is almost entirely governed by the central highlands,
with all the perennial water courses originating in the mountains and winding their way down to the plains below.

气候

Sri Lanka's equatorial position gives its lowlands a tropical climate, with year round
temperatures of 27-28ºC and a relatively constant day length. It is always the right season somewhere on the island Rainfall is largely governed by monsoonal winds, which occur during two seasons
of the year. From mid-May to September, the monsoon blows from the southwest direction and brings in a greater amount of moisture than during December to February when the wind blows from the
northeast. The distinct inter-monsoonal periods receive convectional rains at times cyclones. During the southwest monsoon, the position and dramatic relief of the southwestern side of the
central highlands forces the moisture-laden air upwards. The rapidly cooled air condenses, causing precipitation mostly on the windward slopes of the island’s southwest. During this time the
northeastern and southeastern parts of the island hardly get any rain. On the other hand, the northeast monsoon winds rise over the central highlands more gradually, and the rain shadow effect is
not nearly so distinct, allowing precipitation to fall on the entire island. This has resulted in the division of the country in to two major climatic zones; the wet zone, which receives
rain from both monsoons, and the dry zone, which receives rain from only one. The gradual change from the wet zone to dry zone allows an intermediate zone to exist. In addition,
two small areas at the extreme northwest and southeast of the country have a very dry climate and known as arid zones.

Vegetation types

Vegetation reflects the combined effect of topography, climate and soils. In Sri Lanka the
natural vegetation is predominated by a diversity of forest types. Only a small fraction of land is under non-tree-dominated vegetation. This is mainly grassland, and coastal and fresh water
wetlands.

The most extensive type of forest in the island is the dry mixed evergreen
forest found in the dry zone (also called semi-evergreen forests). In the intermediate zone, the vegetation gradually changes to moist semi-evergreen forests. Although these
forests have a fair proportion of deciduous species, they are essentially evergreen. In the wet zone vegetation has been largely categorised by elevation with wet-evergreen
forests or rain forests in the lowlands and hills, lower montane forests on the lower slopes of mountains between 1,000m and 1,500m, and montane forests above
1500m. Also in the coastal areas mangroves and salt marshes colonise inundated bays while areas inundated by fresh water haveswamp and floodplain forests.

Within each climatic zone, the presence and extent of specific habitat types determine the
occurrence and prevalence of particular species of birds. Within dry zone, for example, habitats such as forests, marshes, grassland, man-made lakes, coastal mudflats etc. harbour certain species
of birds, which are restricted to that specific habitat or are most often associated with it. While some species of birds occur in both zones at all elevations (e.g. Junglefowl) the distribution
of many others is more limited. Many species and subspecies of birds are endemic to Sri Lanka and a significant number of these are more or less restricted to and characteristic of the rain
forests of the wet zone. Some of this wet zone endemics are further restricted to the higher hills.